This invention relates to an improved thermal insulation system for a cargo tank and support structure on board a ship transporting liquefied gas.
While large-scale ocean transport of liquefied gas, in particular liquid natural gas, is becoming a reality, the state of the art in tank insulation systems has not yet reached a satisfactory level in terms of both initial cost and thermal performance. Current engineering technology is principally limited to systems consisting of multi-layered polyurethane or polystyrene foam panels enclosed by an impervious to vapors membrane.
This system performs thermally well as resistance to solid conduction and interstitial gas convection is concerned. However, little consideration has yet been given to resistance to radiation which becomes the predominant mode of heat transfer from surroundings to the insulation system. See, for example, U.S. Pat. Nos. 3,748,865 and 3,828,709.